When the Earth froze over 635-720 million years ago during the “Snowball Earth” period, scientists have long wondered where life might have sheltered from the extreme cold. A new study by MIT researchers suggests that shallow pools of melted ice, or meltwater ponds, could have provided a refuge for ancient eukaryotic life.
The researchers analyzed samples from meltwater ponds on the McMurdo Ice Shelf in Antarctica and found evidence of eukaryotes, complex cellular life forms that eventually evolved into diverse multicellular life. The teams discovered clear signatures of eukaryotic life in every pond, revealing a surprising diversity of life across the setting.
Salinity plays a key role in the kind of life a pond can host, with brackish or salty ponds having more similar eukaryotic communities than those with fresher waters. The study’s findings show that meltwater ponds are valid candidates for where early eukaryotes could have sheltered during these planet-wide glaciation events.
The researchers used lipid analysis and genetic components to identify the types of eukaryotic life present in each pond, revealing a surprising diversity of life across the setting. No two ponds were alike, but there were repeating casts of characters with varying abundances. The study highlights that meltwater ponds during Snowball Earth could have served as above-ice oases that nurtured the eukaryotic life that enabled the diversification and proliferation of complex life – including humans.
The discovery provides a new perspective on the origins of complex life and sheds light on the resilience of ancient organisms in extreme environments. The study’s findings are published in Nature Communications.
Source: https://phys.org/news/2025-06-earth-iced-early-life-meltwater.html